The increased prevalence of obesity and obesity-related diseases among Americans is well documented.^1-3 The overall rate of obesity in adults grew to 30.5% in 1999-2000, from 22.9% in 1988-1994 and less than 15% in the 1970s.¹ The prevalence of morbid, or severe, obesity has increased at a much faster rate than obesity in general.⁴ A substantial body of literature has also shown large financial consequences from obesity. For example, obese adults incur 36% greater annual medical expenditures than normal-weight persons,⁵ and overweight and obesity account for 9.1% of total annual medical expenditures.⁶

Increased prevalence of obesity among the workforce may have several financial consequences for employers.⁷ As increased rates of obesity contribute to rising medical costs, this will likely exacerbate health insurance costs. Recent research has shown that 12% of the rise in inflation-adjusted per capita medical spending between 1987 and 2001 was attributable to the increased prevalence of obesity.⁸ Obese employees have also been shown to be absent from work more often than their nonobese counterparts.^7,9 Thompson et al⁷ found that obese men were absent 2.7 more days per year than normal-weight men, and obese women missed 5.1 more days per year than normal-weight women.

With attention focused on the costs and prevalence of obesity, bariatric surgery—in particular, Roux-en-Y gastric bypass and gastric banding—has recently become a common form of treatment for severe obesity.^10,11 Employers and insurers have, in turn, been forced to make or revisit decisions about coverage for bariatric surgery and other obesity treatments.¹²

Although surgical operations have been shown to be effective in reducing weight and resolving or reducing comorbidities,^13,14 few investigations have addressed potential cost savings resulting from the surgery.¹⁵ Three studies^16-18 applied the conventional cost-effectiveness framework to compute the cost per quality-adjusted life-year for surgery; results ranged from -$4000 per quality-adjusted life-year (net savings)¹⁸ to $35 600 per quality-adjusted life-year.¹⁶

Other studies^19-22 looked at reductions in specific cost components resulting from the surgery, but only 1 study²³ reported the number of years before bariatric surgery results in cost savings, and this study was limited to medical costs in the Canadian healthcare system. The study reported that Roux-en-Y gastric bypass and vertical banded gastroplasty were cost saving after 3.5 years. However, because the Canadian healthcare system is different from the US healthcare system, results may not be generalizable across borders.

In this study, we use nationally representative data for the US full-time employed population to quantify the increase in annual medical costs and work loss associated with obesity among the bariatric surgery-eligible and bariatric surgery-ineligible obese populations. We then use these results in a simulation model to estimate the potential benefits associated with coverage for bariatric surgery under various assumptions. We are aware of no available randomized controlled trial or quasiexperiment with sufficient data to permit a detailed cost-benefit analysis of bariatric surgery. In the absence of such data, a simulation model is feasible and appropriate for providing base-case estimates.

DATA

We used 2 nationally representative data sets of the civilian noninstitutionalized population to quantify annual work loss and medical costs attributable to obesity. We used the 2002 National Health Interview Survey (NHIS) to analyze work loss due to illness or injury and the 2000-2001 Medical Expenditure Panel Survey (MEPS) for medical costs. We applied common sample selection criteria to both data sets. We restricted the sample to individuals aged 18 to 64 years who reported working full time (≥ 35 h/wk) for the entire year. We also excluded pregnant women and individuals with missing body mass index (BMI) data, calculated as weight in kilograms divided by the square of height in meters.

The NHIS is the principal source of information on the health of the household population of the United States. Besides self-reported height, weight, and health conditions, the NHIS includes information on workdays missed due to illness or injury and sociodemographic characteristics, including race and ethnicity, sex, age, education, family size, employment status, occupation, hours of work per week, and income. For analysis of work loss, we began with the 31 044 adults in the 2002 NHIS. After applying the sample restrictions, the final data set included 12 019 full-time employed adults (6641 men and 5378 women) with sampling weights to generate nationally representative estimates. Forty-six percent of the weighted regression population (41% of men and 53% of women) reported missing at least 1 day of work due to illness or injury.

The MEPS sample is a subset of the NHIS participants. The MEPS provides additional details on health conditions and annual medical expenditures, and each individual's data can be merged with his or her responses to the NHIS survey. We used the MEPS and pooled data from 2000-2001 to increase the sample size. Applying the sample selection criteria already detailed reduced the 41 217 (unweighted) adults (17 558 in 2000 and 23 659 in 2001) to the final data set of 20 329 full-time employed adults (11 849 men and 8480 women).

Surgery-eligible obesity was defined as a BMI of 40 or greater, or a BMI of 35 to less than 40 with angina, asthma, osteoarthritis, diabetes mellitus, or hypertension. This approximated the guidelines set by a National Institutes of Health panel on bariatric surgery,²⁴ although the guidelines included other comorbidities that we were unable to measure in our data. Surgery-ineligible obesity was defined as a BMI of 30 to less than 35, or a BMI of 35 to less than 40 without the comorbidities just listed. All other BMI values were considered to represent nonobesity. In the analyses, we included dummy variables for overweight (BMI, 25 to < 30) and underweight (BMI, < 18).

METHODS